Hollow container manufacturing method and manufacturing apparatus

ABSTRACT

A hollow container manufacturing method comprises: an injection molding step of forming a preform having a neck portion and a barrel portion, at least a part of the barrel portion being solid, by injection molding; an intermediate product formation step of inserting a boring rod 134 from the neck portion side into the barrel portion 23 to form a space part of at least a predetermined depth in the barrel portion, thereby converting the preform into an intermediate molded product; and a final blow molding step of blow-molding the intermediate molded product within a final blow mold to form a hollow container which is a final molded product.

TECHNICAL FIELD

This invention relates to a hollow container manufacturing method and ahollow container manufacturing apparatus and, in particular, thosesuitable for the manufacture of an ultrathin container excellent in thedimensional accuracy of a neck.

BACKGROUND ART

Narrow-mouthed hollow containers are utilized, for example, for thestorage of high grade articles expensive and sold in small quantities,such as perfumes, medicines and pills, or for the mailing of samples oftoilet lotions or milky lotions. Known methods for manufacturing suchhollow containers include chose which use blow molding methods such asdirect blow molding using a circular tube-shaped parison; injection blowmolding which comprises injection molding a bottomed tube-shaped preformfollowed by blowing; and injection stretch blow molding (see, forexample, Patent Documents 1 and 2).

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: JP-A-2004-1314

Patent Document 2: Japanese Patent. No. 4051231

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

When a hollow container is to be manufactured by direct blow molding,the problem arises that sealing failure (such as pinholes or defectivewelding) is apt to occur at the bottom of the hollow container. Also,the parison involves the problem that the dimensional accuracy of itsthreaded pare and the smoothness of the top surface of the mouth aregenerally poor. Thus, injection blow molding or injection stretch blowmolding is more suitable than direct blow molding as a molding methodfor a hollow container of which a high dimensional accuracy and anaesthetic appearance are required.

With injection blow molding or injection stretch blow molding, however,there is the problem that a narrow-mouthed hollow container cannot bemolded. The minimum mouth diameter of a hollow container moldable byinjection blow molding or injection stretch blow molding is determinedby the minimum diameter of a core mold for injection molding a preform.Since a cooling circuit or the like needs to be provided inside the coremold, the diameter of the core mold should be of a certain dimension.Thus, the minimum opening diameter of the preform cannot be renderedadequately small and, in accordance with this situation, the minimummouth diameter of the hollow container cannot be rendered sufficientlysmall. Concretely, the minimum mouth diameter of the hollow container isof the order of 4.0 mm at the smallest, and a hollow container of amouth diameter smaller than it has been difficult to mold.

The present invention has been accomplished in the light or theforegoing circumstances. It is an object of the invention to provide ahollow container manufacturing method and a hollow containermanufacturing apparatus which are capable of satisfactorily molding evena narrow-mouthed hollow container.

Means for Solving the Problems

A first aspect of the present invention, aimed at solving the aboveproblems, is a hollow container manufacturing method, comprising: aninjection molding step of forming a preform having a neck portion and abarrel portion, at least a part of the barrel portion being solid, byinjection molding; an intermediate product formation step of inserting aboring rod from a side of the neck portion into the barrel portion toform a space part of at least a predetermined depth in the barrelportion, thereby converting the preform into an intermediate moldedproduct; and a final blow molding step of blow molding the intermediatemolded product to form a hollow container which is a final moldedproduct.

A second aspect of the invention is the hollow container manufacturingmethod according to the first aspect, wherein during the injectionmolding step, a reference hole of a predetermined depth is formed in theneck portion and, during the intermediate product formation step, theboring rod is inserted from the reference hole into the barrel portionto form the space part.

A third aspect of the invention is the hollow container manufacturingmethod according to the second aspect, wherein during the injectionmolding step, the reference hole is formed to a depth reaching thebarrel portion.

A fourth aspect of the invention is the hollow container manufacturingmethod according to any one of the first to third aspects, whereinduring the intermediate product formation step, the space part is formedwith the predetermined depth by inserting the boring rod into the barrelportion while jetting air from at least a leading end of the boring rod.

A fifth aspect of the invention is the hollow container manufacturingmethod according to the fourth aspect, wherein during the intermediateproduct formation step, the space part is formed in the barrel portion,and blow molding is performed so that a barrel portion of theintermediate molded product has a predetermined diameter.

A sixth aspect of the invention is the hollow container manufacturingmethod according to the fourth aspect, wherein the intermediate productformation step and the final blow molding step are uninterruptedlyexecuted to blow-mold the intermediate molded product by air jetted fromthe boring rod, thereby forming the hollow container.

A seventh aspect of the present invention is a hollow containermanufacturing apparatus, comprising: an injection molding section forforming a preform, which has a neck portion and a barrel portion, and inwhich at least a part of the barrel portion is solid, by injectionmolding; an intermediate molding section for inserting a boring rod froma side of the neck portion into the barrel portion to form a space partof at least a predetermined depth in the barrel portion, therebyconverting the preform into an intermediate molded product; and a finalblow molding section for blow molding the intermediate molded product toform a hollow container which is a final molded product.

An eighth aspect of the invention is the hollow container manufacturingapparatus according to the seventh aspect, wherein the boring rod isconfigured to be capable of jetting air from at least a leading endthereof into the barrel portion of the preform.

A ninth aspect of the invention is the hollow container manufacturingapparatus according to the eighth aspect, wherein the boring rod has atthe leading end thereof a ring-shaped opening portion for jetting air.

A tenth aspect of the invention is the hollow container manufacturingapparatus according to any one of the seventh to ninth aspects, whereinthe intermediate molding section is equipped with the boring rod and anintermediate blow mold where the preform is accommodated; and with thepreform being accommodated within the intermediate blow mold, the boringrod is inserted into the barrel portion to form the space part, and blowmolding is performed so that the barrel portion has a predetermineddiameter.

An eleventh aspect of the invention is the hollow containermanufacturing apparatus according to any one of the seventh to ninthaspects, wherein the final blow molding section concurrently serves asthe intermediate molding section; the final blow molding section isequipped with the boring rod and a final blow mold; in the final blowmolding section, with the preform being accommodated within the finalblow mold, the boring rod is inserted into the barrel portion to formthe space part, thereby converting the preform into the intermediatemolded product, and the intermediate molded product is uninterruptedlyblow-molded to form the hollow container.

Effects of the Invention

With the present invention as described above, there is no need toprovide a cooling circuit within the core mold for injection molding thepreform. Thus, the diameter of the core mold can be decreased incomparison with conventional technologies. Hence, the minimum diameterof the preform can be rendered small, and the minimum mouth diameter ofthe hollow container can be made small. That is, the present inventionpermits satisfactory molding of not only a hollow container with arelatively large mouth diameter, but also a narrow-mouthed hollowcontainer having a very small mouth diameter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an example of a hollow container.

FIG. 2 is a sectional view of the example of the hollow container.

FIGS. 3 (a), 3(b) are sectional views of an injection molded preform.

FIG. 4 is a block diagram showing the schematic configuration of ahollow container manufacturing apparatus according to an embodiment ofthe invention.

FIG. 5 is a schematic sectional view illustrating an injection stepaccording to the embodiment.

FIGS. 6(a) to 6(c) are schematic sectional views illustrating anintermediate product formation step in the embodiment.

FIGS. 7(a), 7(b) are sectional views showing modifications of a boringrod.

FIG. 8 is a schematic sectional view illustrating a final blow moldingstep in the embodiment.

FIG. 9 is a block diagram showing another example of the hollowcontainer manufacturing apparatus according to the embodiment.

FIGS. 10(a), 10(b) are schematic sectional views illustrating anotherexample of the final blow molding step according to the embodiment.

MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will now be described in detailby reference to the accompanying drawings.

FIG. 1 is a perspective view showing an example of a hollow container,and FIG. 2 is a sectional view thereof.

A hollow container 10 shown in FIG. 1 and FIG. 2 is composed of a neck12 having a mouth at the upper end, a tubular barrel 13 continuous withthe neck 12, and a bottom continuous with the barrel 13. The hollowcontainer 10 is a small container, for example, used as a sample storinga toilet lotion or a milky lotion, and the mouth 11 is formed with avery small opening diameter, for example, of the order of 2 to 3 mm. Inthe present embodiment, the bottom 14 of the hollow container 10 isformed with a larger wall thickness than that, of the barrel 13. Thatis, the wall thickness of the barrel 13 is formed to be small ascompared with the bottom 14. The material for the hollow container 10 isnot particularly limited, but polyethylene terepthalate (PET), forexample, is used preferably.

By shaping the hollow container 10 as above, it can be made to fit, forexample, an image which consumers have of a cosmetics container. Thatis, such a shape can improve the aesthetic appearance of the hollowcontainer 10, so that the hollow container 10 can be used as a cosmeticscontainer or the like for which a good look is important.

The hollow container 10 with the mouth 11 of a very small diameter canbe manufactured by a hollow container manufacturing method according tothe present invention which will be described below.

As shown, in FIGS. 3(a), 3(b), the hollow container manufacturing methodaccording to the present invention molds the hollow container 10 (seeFIG. 2), which is a final molded product, by way of a preform 20 and anintermediate molded product 30 having predetermined shapes.

The preform 20 according to the present embodiment, as shown in FIG.3(a), has a neck portion 22 formed with a threaded groove 21 on theouter periphery, and a barrel portion 23 continuous with the neckportion 22. The neck portion 22 of the preform 20 is provided with areference hole 24 of a predetermined depth opening to the upper end (topsurface). In the present embodiment, the reference hole 24 is formed tosuch a depth as to reach the barrel portion 23 through the neck portion22. The barrel portion 23 of the preform 20 is solid almost entirely. Inother words, the barrel portion 23 of the preform 20 is filled with amolding material entirely in its axial direction, and is formed in asubstantially cylindrical shape, rather than in a tubular shape having aspace inside.

A preform for forming a hollow container, generally, refers to oneformed by injection molding and having a neck portion and a bottomedtube-shape barrel portion. The preform 20 according to the present,invention, on the other hand, refers to one formed by injection moldingand having the neck portion 22 and the substantially solid barrelportion 23, as mentioned above. Hence, the preform according to thepresent invention includes, for example, one which is formed byinjection molding and composed of a solid barrel position and a solidneck portion where no reference hole is formed.

The intermediate molded product 30 has a neck portion 32 of the sameshape as that of the neck portion 22 of the preform 20, and a barrelportion 33 continuous with the neck portion 32, as shown in FIG. 3(b).In the neck portion 32 of the intermediate molded product 30, a mouthportion 34 constituted by the reference hole 24 and opening to the upperend is formed. The barrel portion 33 of the intermediate molded product30 is furnished with a space part 35 formed by inserting a boring rod(to be described later) through the reference hole 24 into the barrelportion 33. That is, the intermediate molded product 30 according to thepresent invention refers to one provided with the space part 35 formedby inserting the boring rod into the barrel portion 33. The space part35 refers to one formed by at least the insertion of the boring rod, andincludes, for example, one formed by blow molding as well as theinsertion of the boring rod. In the present embodiment, the space part35 is formed by inserting the boring rod and performing blow molding, aswill be described later. As a result, the diameter of the barrel portion33 is larger than the diameter of the barrel portion 23 of the preform20, and the diameter of the space part 35 is larger than the diameter ofthe mouth portion 34.

A hollow container manufacturing apparatus (molding apparatus) 100according to the present embodiment has an injection molding section 120connected to an injection device 110, an intermediate molding section130, a final blow molding section 140, and a withdrawal section 150, forexample, as shown in FIG. 4. That is, the hollow container manufacturingapparatus 100 has a 4-station structure, for example, as disclosed inJapanese Patent No. 3722671. As will be described in detail later, thefirst step is to form the preform 20 of a predetermined shape byinjection molding in the injection molding section 120 (injectionmolding step). This preform 20 is transported to the intermediatemolding section 130, where the intermediate molded product 30 is formedfrom the preform 20 (intermediate production formation step). Theintermediate molded product 30 is transported to the final blow moldingsection 140, where the intermediate molded product 30 is blow-molded toform the hollow container 10 which is a final molded product (final blowmolding step). Then, the hollow container 10 is transported to thewithdrawal section 150, and withdrawn from the withdrawal section 150 tothe outside of the manufacturing apparatus 100.

Concretely, in the injection molding section 120, the preform 20 of thepredetermined shape mentioned above is formed using an injection mold121, as shown in FIG. 5. The injection mold 121 is composed of a neckmold 122 which defines the outer peripheral surface of the neck portion22 of the preform 20 and comprises an openable and closable split mold;an injection cavity mold 123 defining the outer peripheral surface ofthe barrel portion 23; and an injection core mold 124 defining the innerperipheral surface of the preform 20, i.e., the inner peripheral surfaceof the neck portion 22 in the present embodiment. An injection space 125is formed by the neck mold 122, the injection cavity mold 123, and theinjection core mold 124.

A resin material (e.g., PET resin) as a raw material is charged into theinjection space 125 via a gate 126 provided at the center of the bottomof the injection cavity mold 123, whereby the preform 20 as describedabove is formed.

The preform 20 according to the present embodiment has the barrelportion 23 formed to be solid. Even without cooling after injectionmolding, therefore, the preform 20 can be transported to theintermediate molding section 130, after the barrel portion 23 isreleased from the injection mold 121, with the neck portion 22 beingheld by the neck mold 122. That is, the preform 20 is ensured of havingsuch strength that even without, cooling after injection molding, thebarrel portion 23 can be released from the injection mold 121 andcarried to the intermediate molding section 130. In short, the barrelportion 23 of the preform 20 is formed to be solid at least partly sothat the above strength of the preform 20 can be secured. In otherwords, the reference hole 24 of the preform 20 is formed with asufficient depth to be capable of ensnaring such a strength.

In the intermediate molding section 130, as shown in FIGS. 6(a) to 6(c),the preform 20 is disposed, within an intermediate blow mold 131 (FIG.6(a)), where the intermediate molded product 30 is formed from thepreform 20 (see FIG. 6(b), FIG. 3(b)).

The intermediate blow mold 131 is equipped with a neck mold 132 forholding the neck portion 22 (32), an intermediate blow molding splitmold 133, and a boring rod 134 to be inserted from the side of the neckportion 22 of the preform 20, that is, inserted via the reference hole24 into the barrel portion 23. The boring rod 134 is provided to beupwardly and downwardly movable, and is configured to be capable ofejecting a gas, such as air, from its leading end. In the presentembodiment, as indicated by a sectional view of FIG. 6(c), the boringrod 134 is composed of a cylindrical first member 135, and a rod-shapedsecond member 136 inserted into the first member 135, and a ring-shapedflow path space (opening) 137 is formed between the first member 135 andthe second member 136. From the leading end of the boring rod 134, airjets (eject, gushes) to the outside via the ring-shaped flow path space137.

In the intermediate molding section 130 equipped with the aboveintermediate blow mold 131, the boring rod 134 is inserted from the sideof the neck portion 22 of the preform 20 into the barrel portion to formthe space part 35 of the predetermined depth within the barrel portion23 to form the intermediate molded product 30, as shown in FIG. 6(b).The barrel portion 23 is maintained at a relatively high temperature (itpossesses ample residual heat derived from injection molding), and isnot completely cured (hardened). Thus, the space part 35 can be formedsatisfactorily by inserting the boring rod 134. When the boring rod 134is inserted into the barrel portion 23 of the preform 20, moreover, airis jetted from the leading end of the boring rod 134. Hence, while theresin is being pushed away by this air, the space part 35 can be formedwell.

In the present embodiment, moreover, the barrel portion 33 (23) isblow-molded by air jetting from the leading end of the boring rod 134.That is, the barrel portion 33 (23) is stretched in the lateral axisdirection, and pressed against the intermediate blow molding split mold133, by the high pressure air jetting from the boring rod 134. As aresult, the diameter of the barrel portion 33 of the intermediate moldedproduct 30 becomes larger than the diameter of the barrel portion 23 ofthe preform 20, and the diameter of the space part 35 becomes largerthan the diameter of the mouth portion 34 (see FIG. 3(b)).

The boring rod 134 may be changed, as appropriate, so as to match theexternal appearance of the hollow container 10, which is the finalmolded product, and the inner surface shape of the space part 35 whichis to be imparted. If the cross-sectional shape of the barrel of thehollow container 10 is elliptical, for example, the cross-sectionalshape of the boring rod 134 may be nearly elliptical. Concretely, theboring rod 134 may be composed of a cylindrical first member 135A of anearly elliptical cross-sectional shape, and a rod-shaped second member136A of a nearly perfectly circular cross-sectional shape, for example,as shown in FIG. 7(a).

Alternatively, as shown in FIG. 7(b), for example, the boring rod 134may be composed of a cylindrical first member 135B of a nearly perfectlycircular cross-sectional shape, and a rod-shaped second member 136Binserted through the first member 135B and having chamfered sidesurfaces (having a nearly elliptical cross-sectional shape). In thisconfiguration, the flow path in which air jets is defined in apredetermined direction. Even if the hollow container 10 is to beprovided with a complicated external shape, such as an elliptical shape,therefore, it can be shaped appropriately. It is also permissible toconfigure the first member 135 and the second member 136 constitutingthe boring rod 134 so as to be drivable independently of each other,with a view to improving the degree of freedom of molding.

The manufacturing apparatus 100 according to the present embodiment is aso-called one-stage molding apparatus, in which the preform 20injection-molded in the injection molding section 120 is transported tothe intermediate molding section 130 while being maintained at arelatively high temperature. The barrel portion 23 of the preform 20, inparticular, minimally lowers in temperature, because it is solid. In thepresent embodiment, moreover, the reference hole 24 is formed with adepth reaching the barrel portion 23 involving a minimal fall intemperature. In the intermediate molding section 130, therefore, thespace part 35 can be formed satisfactorily by inserting the boring rod134 into the barrel portion 23, without heating the preform 20.

In the intermediate molding section 130, needless to say, the preform 20may be heated to a predetermined temperature (temperature-controlled),if necessary, before or during the placement of the preform 20 withinthe intermediate blow molding split mold 133.

If the manufacturing apparatus 100 is the 1-stage apparatus, it isdesirable that the reference hole 24 be formed with such a relativelyshallow depth as to reach the barrel portion 23. By so doing, thetemperature fall of the barrel portion 23 during the transport of thepreform 20 to the intermediate molding section 130 can be suppressed. Ifthe manufacturing apparatus 100 is a so-called 2-stage moldingapparatus, namely, if the injection-molded preform 20 is once cooled, onthe other hand, it is preferred that the reference hole 24 be formedrelatively deeply. By so doing, the preform 20 is easily reheated. Thedepth of the reference hole 24 is not particularly limited, and may bedetermined, as appropriate, in consideration of the deformation(strength), etc. of the preform 20 during mold release.

Then, the intermediate molded product 30 is transported to the finalblow molding section 140 and, as shown in FIG. 8, is disposed within afinal blow mold 141 heated to a predetermined temperature. The finalblow mold 141 is equipped with a neck mold 142 for holding the neckportion 32 of the intermediate molded product 30, and anopenable/closable final blow molding split mold 143.

Within the final blow mold 141, the intermediate molded product 30 isblow-molded to obtain the hollow container 10 which is the final moldedproduct (see FIG. 2). That is, high pressure air is introduced from theneck portion 32 (mouth portion 34) into the barrel portion 33 (spacepart 35) of the intermediate molded product 30 disposed within the finalblow mold 141, whereby the barrel portion 33 is stretched and pressedagainst the final blow molding split mold 143. As a result, the hollowcontainer 10, which is the final molded, product of a desired shape, ismolded (see FIGS. 1 and 2). In the final blow molding section 140, forthe purpose of preventing positional displacement of the intermediatemolded product 30 or stretching it positively in the vertical axisdirection, for example, it is acceptable to adopt a mode in which a rodis inserted from the neck portion 32 into the space part 35 and, in thisstate, the intermediate molded product 30 is blow-molded to form thehollow container 10.

According to the hollow container manufacturing method concerned withthe present embodiment, as described above, the preform 20 is formed sothat the barrel portion 23 becomes substantially solid. Thus, with theneck portion 22 being held, but without cooling of the preform 20, thebarrel portion 23 can be released from the injection mold 121, andtransported to the intermediate molding section 130. Hence, there is noneed to provide a cooling circuit or the like within the injection coremold 124 defining the inner surface of the preform 20 at the time ofinjection molding. Thus, the diameter of the injection core mold 124 canbe decreased in comparison with the diameter of the conventional one.Since the diameter of the injection core mold 124 can be made small, themouth 11 of the hollow container 10 can also be thinned extremely.

This means that the present invention enables the satisfactory moldingof not only a hollow container with a relatively large mouth diameter,but also a narrow-mouthed hollow container with a very small mouthdiameter.

In the present embodiment, the bottom 14 of the hollow container 10 isformed to have a larger wall thickness than that of the barrel 13. Inmolding the hollow container 10 of such a shape, the bottom portion ofthe preform 20 or the intermediate molded product 30 is also formed tohave a larger wall thickness than that of the barrel portion. In thepresent invention, as stated above, the boring rod 134 is inserted intothe barrel portion 23 of the preform 20 to form the space part 35. Forthis reason, the wall thickness of the bottom portion of the preform 20can be adjusted relatively easily. Thus, even a hollow container havinga bottom of a larger wall thickness than the wall thickness of a barrelcan be formed with high precision.

According to the hollow container manufacturing method concerned withthe present invention, as described above, the hollow container 10 canbe formed with an attractive appearance, regardless of the shape of thehollow container 10, and can be used as a container for cosmetics, forexample.

The present invention has been described above in connection, with itsembodiment, but it goes without saying that the invention is in no waylimited to this embodiment. The present invention can be changed ormodified appropriately without departing from its scope and spirit.

In the foregoing embodiment, for example, the reference hole of a depthreaching the barrel portion is formed in the preform, but the depth ofthis reference hole is not particularly limited. The reference hole isdesirably provided even if shallow, for example, for positioning of theboring rod, but need not necessarily be provided.

In the above embodiment, for example, the intermediate molded product isformed from the preform, and the intermediate molded product isblow-molded to form the hollow container which is the final moldedproduct. However, the molding procedure is not limited to thisprocedure. For example, it is permissible to inject-mold the preform,then inset the boring rod into the preform to form the space part,thereby converting the preform into the intermediate molded product, andthen uninterruptedly blow-mold the intermediate molded product to formthe hollow container which is the final molded product,

For example, the final blow molding section 140 of the hollow containermanufacturing apparatus 100 may concurrently serve as the intermediatemolding section. Concretely, the hollow container manufacturingapparatus 100 may be composed of the injection molding section 120, thefinal blow molding section 140 also serving as the intermediate moldingsection, and the withdrawal section 150, as shown in FIG. 9. That is,the manufacturing apparatus 100 may be of a 3-station structure asdisclosed in JP-B-5-32211. In this case, the preform 20 injection-moldedin the injection molding section 120 is disposed within the final blowmold 141 of the final blow molding section 140, as shown in FIG. 10(a).Then, a boring rod 144, which the final blow mold 141 has, is insertedfrom the side of the neck portion 22 of the preform 20 into the barrelportion 23 to form the space part 35 of a predetermined depth and turnthe preform 20 into the intermediate molded product 30, as shown in FIG.10(b). Uninterruptedly, the intermediate molded product 30 isblow-molded by air jetting (gushing) from the leading end of the boringrod 144. As a result, the hollow container 10 as the final moldedproduct is obtained (see FIG. 2). The manufacturing apparatus 100 mayalso be configured such that the final blow molding section 140 furtherhas the withdrawal section 150. That is, the manufacturing apparatus 100may be of a 2-station structure as disclosed in Japanese Patent No.2530398.

In the above-mentioned embodiment, the cylindrical hollow container 10with the bottom having a larger wall thickness than that of the barrelis illustrated. However, the shape of the hollow container 10 is notparticularly limited. For example, the bottom of the hollow containermay have the same wall thickness as that of the barrel, and the hollowcontainer need not be cylindrical.

EXPLANATIONS OF LETTERS OR NUMERALS

-   10 Hollow container-   11 Mouth-   12 Neck-   13 Barrel-   14 Bottom-   20 Preform-   21 Threaded groove-   22 Neck portion-   23 Barrel portion-   24 Reference hole-   30 Intermediate molded product-   32 Neck portion-   33 Barrel portion-   34 Mouth portion-   35 Space part-   100 Manufacturing apparatus (molding apparatus)-   110 Injection device-   120 Injection molding section-   121 Injection mold-   122 Neck mold-   123 Injection cavity mold-   124 Injection core mold-   125 Injection space-   126 Gate-   130 Intermediate molding section-   131 Intermediate blow mold-   132 Neck mold-   133 Intermediate blow molding split mold-   134 Boring rod-   135 First member-   136 Second member-   137 Flow path space-   140 Final blow molding section-   141 Final blow mold-   142 Neck mold-   143 Final blow molding split mold-   144 Boring rod-   150 Withdrawal section

The invention claimed is:
 1. A hollow container manufacturing method,comprising: an injection molding step of forming a preform having a neckportion and a barrel portion, at least a part of the barrel portionbeing solid, by injection molding; an intermediate product formationstep of inserting a boring rod from a side of the neck portion into thebarrel portion to form a space part of at least a predetermined depth inthe barrel portion, thereby converting the preform into an intermediatemolded product; and a final blow molding step of blow molding theintermediate molded product to form a hollow container which is a finalmolded product.
 2. The hollow container manufacturing method accordingto claim 1, wherein during the injection molding step, a reference holeof a predetermined depth is formed in the neck portion, and during theintermediate product formation step, the boring rod is inserted from thereference hole into the barrel portion to form the space part.
 3. Thehollow container manufacturing method according to claim 2, whereinduring the injection molding step, the reference hole is formed to adepth reaching the barrel portion.
 4. The hollow container manufacturingmethod according to claim 1, wherein during the intermediate productformation step, the space part is formed with the predetermined depth byinserting the boring rod into the barrel portion while jetting air fromat least a leading end of the boring rod.
 5. The hollow containermanufacturing method according to claim 4, wherein during theintermediate product formation step, the space part is formed in thebarrel portion, and blow molding is performed so that a barrel portionof the intermediate molded product has a predetermined diameter.
 6. Thehollow container manufacturing method according to claim 4, wherein theintermediate product formation step and the final blow molding step areuninterruptedly executed to blow-mold the intermediate molded product byair jetted from the boring rod, thereby forming the hollow container. 7.A hollow container manufacturing apparatus, comprising: an injectionmolding section for forming a preform, which has a neck portion and abarrel portion, and in which at least a part of the barrel portion issolid, by injection molding; an intermediate molding section forinserting a boring rod from a side of the neck portion into the barrelportion to form a space part of at least a predetermined depth in thebarrel portion, thereby converting the preform into an intermediatemolded product; and a final blow molding section for blow molding theintermediate molded product to form a hollow container which is a finalmolded product.
 8. The hollow container manufacturing apparatusaccording to claim 7, wherein the boring rod is configured to be capableof jetting air from at least a leading end thereof into the barrelportion of the preform.
 9. The hollow container manufacturing apparatusaccording to claim 8, wherein the boring rod has at the leading endthereof a ring-shaped opening portion for jetting air.
 10. The hollowcontainer manufacturing apparatus according to claim 7, wherein theintermediate molding section is equipped with the boring rod and anintermediate blow mold where the preform is accommodated, and with thepreform being accommodated within the intermediate blow mold, the boringrod is inserted into the barrel portion to form the space part, and blowmolding is performed so that the barrel portion has a predetermineddiameter.
 11. The hollow container manufacturing apparatus according toclaim 7, wherein the final blow molding section concurrently serves asthe intermediate molding section, the final blow molding section isequipped with the boring rod and a final blow mold, and in the finalblow molding section, with the preform being accommodated within thefinal blow mold, the boring rod is inserted into the barrel portion toform the space part, thereby converting the preform into theintermediate molded product, and the intermediate molded product isuninterruptedly blow-molded to form the hollow container.